1. Field of the Invention
The present invention relates generally to a system for controlling the bed level of a fluidized bed, and more particularly to a system for controlling such a bed level which is independent of the density of the bed material.
2. Description of the Related Art
Various methods have been utilized to control the bed level of a fluidized bed. Typically, such methods require the use of a multiplicity of pressure sensors connected to pressure sensing taps located a small distance apart. If a pressure sensor senses a pressure higher than that sensed by the pressure sensor immediately above it, then it is known that the bed level is between these two pressure sensors. The foregoing method has many inherent disadvantages in that a large number of pressure sensors, taps, and sensing lines are required, and the resolution of the system is limited by the distance between adjacent prassure sensing taps. Other measuring systems which use fewer pressure sensing locations require that the density of the bed material be known in order to determine the bed level of the fluidized bed.
Because of the foregoing, it has become desirable to develop a control system which accurately indicates the bed level of a fluidized bed independent of the density of the bed material and with a minimum number of pressure sensors.